Got a weird one. I cast Baleful Eidolon for GB, AI took it with Perplexing Chimera... so far, so good... then I click my Whip of Erebos to see if there's anything in my graveyard... there isn't, but Forge untaps the Swamp that I used to cast Baleful Eidolon and also puts B in my mana pool. I end up with two more mana than I should have.

Xyx wrote:Got a weird one. I cast Baleful Eidolon for GB, AI took it with Perplexing Chimera... so far, so good... then I click my Whip of Erebos to see if there's anything in my graveyard... there isn't, but Forge untaps the Swamp that I used to cast Baleful Eidolon and also puts B in my mana pool. I end up with two more mana than I should have.

Hmm, yeah, there are some weird long-standing issues with mana refunding, some of them exploitable (e.g. with stuff that produces two mana for a certain cost). Not sure how to fix them yet, and no one's been able to address them so far (most likely it requires a rewrite of the whole mana payment subsystem). They're not incredibly common, and most of them require you to "want to cheat" in order to actually exploit them (vs. ignoring them), but yes, they're there. Hopefully someone will eventually get an insight as to how to fix this stuff.

Comprehensive Rules wrote:119.8. If a source would deal 0 damage, it does not deal damage at all. That means abilities that trigger on damage being dealt won’t trigger. It also means that replacement effects that would increase the damage dealt by that source, or would have that source deal that damage to a different object or player, have no event to replace, so they have no effect.